1. Field of the Invention
The present invention relates to a balun that performs conversion between unbalanced and balanced signals, and in particular relates to a thin film balun that is formed by a thin film process advantageous for smaller and thinner models.
2. Description of the Related Art
A wireless communication device includes various high frequency elements such as an antenna, a filter, an RF switch, a power amplifier, an RF-IC, and a balun. Of these elements, a resonant element such as an antenna or a filter handles an unbalanced signal which is based on a ground potential, whereas an RF-IC which generates or processes a high frequency signal handles a balanced signal. Accordingly, when connecting these two elements, a balun that functions as an unbalanced-balanced converter is used.
In design of the above-mentioned balun, lengths and shapes of coils (line portions) are optimized so that desired balance characteristics can be achieved in signal frequencies which are subject to conversion, while maintaining the miniaturization of the balun in order to meet recent demands for smaller electronic devices (for example, see Japanese Patent No. 3800121).